Radiation shield structures and their production



United States Patent ce 3,039,000 RADIATION SHIELD STRUCTURES AND THEIRPRODUCTION Richard Kielfer and Karl Sedlatschek, Reutte, Tirol, 5Austria, assignors to Schwarzkopf Development Corporation, New York,N.Y., a corporation of Maryland 7 .No' Drawing. Filed Sept. 6, 1957,Ser. No. 682,294

1 '4 Claims. (Cl. 250108) This invention relates to radiation shields ofthe type required for intercepting radiation from radioactivesubstances, X-ray, and the like radiation sources, including isotopecontainers.

In the past, lead and a solid solution of tungsten, copper and nickelhave been principally used as radiation shields for interceptingradiation of such radiation sources.

The present invention is based on the discovery that a solid solution oralloy of tungsten and uranium of a composition containing essentially50% to 95% tungsten and 5% to 50% of uranium or uranium-rich alloys,provides an ideal radiation shield for such radiation sources. As usedherein in the specification and claims, all proportions are given byweight.

The desired alloys or solid solutions of tungsten and uranium, oruranium alloys, may be provided in a variety of ways. As an example,powder particles of tungsten are compacted, and the tungsten powdercompact is infiltrated with molten uranium or a molten uranium alloy, bymelting an infiltrant body of uranium or uranium alloy While it is incontact with the porous tungsten compact, and heating the contactingparts until the uranium content difiuses and forms a solid solution withthe tungsten content. The heating and infiltration of the compact andthe uranium or uranium alloy is carried on in an oxidatiomsuppressingspace such as either under vacuum or under an atmosphere of noble gassuch as argon or helium. The tungsten powder compact may be sinteredbefore subjecting it to infiltration and diliusion with the uranium oruranium alloy infiltrant.

Alternatively, the desired shield may be produced out of a mixture ofpowder particles of tungsten and powder particles of uranium or uraniumalloy, by compacting the properly proportioned mixture of such differentmetal particles and heating the compact to a temperature at ,7

which the uranium or uranium alloy content of the compact forms a liquidphase which fills all the pores of the compact, and its tungsten anduranium contents diffuse or form a solid solution with each other.

Such infiltrated and diffused or compacted and diffused compacts of 50%to 95% tungsten and 5% to 50% uranium, exhibit a density of about 19,and they may be readily machined by standard metal shaping machines suchas millers, lathes, drills, grinders, polishers, and the like.

Below are given specific examples of desirable radiation shield bodiesof the invention:

Example 1 Powder particles of tungsten are compacted in a die cavityhaving the shape of the desired shield structure, such as a shieldcontainer, to provide a compact having 40% porosity, or the pores ofwhich form 40% of itsv volume. An infiltrant body of uranium is broughtin contact with the tungsten compact, and the composite aggregate soformed is placed in an infiltrating furnace the space of which ismaintained under vacuum until the compact and the infiltrant are heatedwithin 50 C. to 100 C. above the melting temperature of the uraniuminfiltrant so as to cause it to melt and infiltrate into the pores ofthe compact; The infiltrating compact is maintained in such furnacespace at the raised infiltrating tempera- 3,039,fi00 Patented June 12,1962 is thus obtained a shield body consisting of tungstenuranium alloycontaining approximately 60% tungsten and 40% uranium. Example 2 Powderparticles of tungsten are compacted in a suitable die into a cylindricalcompact which is then sintered at 1000 C. to yield a sintered tungstencompact, the pores of which constitute 12% of its volume. An infiltrantbody of uranium having a volume corresponding to the pores of thetungsten compact is placed in contact with the tungsten compact. Thecompact with the infiltrant in contact therewith is heated in a furnaceunder vacuum to above the melting temperature of the infiltrant, therebymelting the infiltrant and causing it to infiltrate all the pores of thetungsten compact. The infiltrated compact is kept in the furnace undervacuum until all the tungsten and uranium content of the compact diffuseand form a solid solution with each other. The resulting shield bodyconsists of an alloy containing tungsten and 10% uranium.

Example 3 There are prepared powder particles of a uraniumaluminum alloycontaining 90% uranium and 10% aluminum. A mixture of 80% of tungstenpowder particles and 20% of such uranium-aluminum alloy particles isthen compacted in the die cavity of a suitable die to provide a compactof the desired shape. The resulting shaped compact is then heated in afurnace under an atmosphere of noble gas such as argon, maintained belowatmospheric pressure, until all the different metal contents of thecompact diffuse and go into solid solution with each other. Theresulting body consists of a tungsten-uranium-aluminum alloy, containingabout 80% tungsten, 18% uranium and 2% aluminum.

Bodies similar to those described above may be made with uranium alloyscontaining as an alloying metal up to 10% aluminum.

The new radiation shield bodies of the invention described above are notonly efiective as shields for intercepting radiation from radioactivesources, but they are also desirable for other applications. Thus, thefiact that they may be readily machined, makes it possible to use suchbodies in applications requiring heavy metal bodies, such as balancingweights, fly weights, and the like.

The features and principles underlying the invention described above inconnection with specific exemplifications will suggest to those skilledin the art many other modifications thereof. It is accordingly desiredthat the appended claims shall not be limited to any specific featuresor details shown and described in connection with the exemplificationsthereof.

We claim:

1. In combination with a body containing a source of nuclear radiation,a radiation shield surrounding said body for intercepting radiation fromsaid body, comprising a shaped shield structure having 100% density andconsisting essentially of 50% to tungsten alloyed with 50% to 5%uranium, said shield structure consisting of a sintered skeleton ofpowder particles formed of the tungsten content of said body, and aninfiltrant metal consisting of uranium filling all the pores of saidskeleton, the infiltrated skeleton having been heated to cause asubstantial amount of the tungsten and infiltrant metal of the body todiffuse into and form a solid solution with each other.

2. In combination with a body containing a source of nuclear radiation,a radiation shield surrounding said body for intercepting radiationtherefrom comprising a shaped shield structure having 100% density andconsisting essentially of 80% to 95% tungsten alloyed with 20% to 5% ofuranium, said shield structure consisting of a :sintered porous skeletonof powder particles consisting essentiallyof tungsten and an infiltrantmetal consisting principally of uranium filling all the pores of saidsintered skeleton, the uranium-infiltrated skeleton having been heatedto cause a substantial amount of the infiltrant metal to diffuse intoand form a solid solution with the tungsten of said skeleton.

3. The combination as claimed in claim ,2, the uranium of saidinfiltrant containing up to 10% of aluminum.

4. The combination as claimed in claim 2, all of said infiltrant metalconsisting essentially of uranium.

References Cited in the file of this patent UNITED STATES PATENTS MaidenMay 22, 1928 Reinhardt Sept. 20, 1932 Kochring Oct. 19, 1937 Henzel eta1. May 10, 1949 Kurtz May 31, 1949 Morrison Dec. 25, 1951 Swift Oct.12, 1954 Rough et a1. Feb. 21, 1956 Keeler et al. Apr. 24, 19 56 TittleNov. 6, 1956

1. IN COMBINATAION WITH A BODY CONTAINING A SOURCE OF NUCLEARRADIATAION, A RADIATION SHIELD SURROUNDING SAID BODY FOR INTERCEPTINGRADIATION FROM SAID BODY, COMPRISING A SHAPED SHIELD STRUCTURE HAVING100% DENSITY AND CONSISTING ESSENTIALLY OF 50% TO 95% TUNGSTEN ALLOYEDWITH 50% TO 5% URANIUM, SAID SHIELD STRAUCTURAE CONSISTING OF A SINTEREDSKELETON OF POWDER PARATICLES FORMED OF THE TUNGSTEN CONTENT OF SAIDBODY, AND AN INFILTRAANT METAL CONSISTING OF URANIUM FILLING ALL THEPORAES OF SAID SKELETON THE INFILTRATED SKELETON HAVING BENN HEATED TOCAUSE A SUBSTANTIAL AMOUNT OF THE TUNGSTEN AND INFILTRAANT METAL OF THEBODY TO DIFFUSE INTO AND FORM A SOLID SOLUTION WITH EACH OTHER.